Future mobile telecommunication systems such as UMTS define three operational states for mobile terminals. These are: an “Idle” state in which the terminal is not active, e.g. it is switched off or otherwise not registered with the network; a “Connected” state in which the terminal is switched on and registered with the network but is not currently involved in a communication session; and an “Active” state in which the terminal is switched on, registered with the network, and currently involved in a communication session.
There exists a desire in the telecommunications industry and amongst consumers to enable mobile wireless terminals to send and receive Internet Protocol (IP) data to and from the Internet and other IP networks. There is also a desire to allow mobile terminals to be in an “Always On” state, whereby the terminals can initiate the sending and receiving of IP data when in a Connected state (as well of course as in an Active state) without the need for a “full-blown” connection set-up phase, other than the set-up phase required when the terminals are initially powered-up. The “Always On” state requires the permanent allocation of an IP address to a mobile terminal, at least for the time that the mobile terminal is switched on, and eliminates the need for a connection set-up phase each time an Internet session is initiated.
The traditional Always On concept will allow the provision of “push-services” where data may be sent to a mobile terminal without any direct initiation by the subscriber. Examples of push services are the delivery of up to the minute news and stock market information to mobile subscribers. A permanent IP address as provided for in the Always On concept may also be required for longer term data transfer such as during a working session, e.g. multiple file transfers, the sending/fetching of e-mails, etc.
In order to have IP access, a mobile wireless terminal must have allocated to it a globally unique IP address. According to the Always On concept, a mobile wireless terminal, which is registered for example with a GSM or UMTS telecommunications network comprising a General Packet Radio Service (GPRS) network, will be allocated a globally unique IP address upon registration by a control node, referred to below as an “Access Control Point” (ACP). An ACP is in fact an enhanced Media Gateway Controller (MGC).
The ACP can be regarded as a server node (or group of nodes) which takes part in certain control plane operations such as mobility management (MM) and session management. The ACP may control one or more Gateway nodes which handle user data. The proposed UMTS architecture for packet switched services is illustrated in FIG. 1 (n.b. if the HLR and ACPs are in different networks, the networks are referred to respectively as the “home” network and the “foreign” network), where the leftmost ACP node corresponds to a Serving GPRS Support Node (SGSN) and the rightmost node corresponds to a Gateway GPRS Support Node (GGSN). The IP address allocated by the ACP will be allocated to the mobile terminal until such time as the terminal de-registers from the ACP (e.g. the power is switched off or the terminal leaves the coverage area of the ACP).
In a modification to the architecture of FIG. 1, the gateway node may be integrated into the Radio Network Controller (RNC) node. The ACP may or may not be part of the RNC node. This modified architecture is referred to below as a “Direct Internet Access” (DIA) architecture.
Assuming that many hundreds of thousands (or even millions) of mobile terminals are registered with a network and are in the Always On state, problems may arise due to the limited address space available with IP (especially with IPv4). Additionally, allocated IP addresses require storage and processing capacity in the routers and gateway nodes of mobile networks. An allocated IP address must be reserved for a mobile terminal even if the terminal is not engaged in a call, in order to enable the transfer of downlink traffic to the terminal and to allow for real “Always On” service. Furthermore, maintaining unused active “contexts” in a gateway means wasted processing and storage capacity.
Another problem related to the conventional Always On architecture is the resulting increased volume and complexity of Mobile IP (MIP) related mobility management signalling traffic. If MIP protocols are used for handling mobility management within a mobile network, the network must allocate a new IP address (care-of-address) to a terminal when it roams in the network. The volume of mobility management signalling traffic increases as, in addition to notifying the Home Location Register (HLR) of its current location, the mobile terminal must also inform its Home Agent (which is responsible for routing datagrams from the home network to roaming terminals) of its current IP address, even if the terminal is not engaged in a call.
Yet another problem associated with the Always On concept is a possible decrease in the level of a user's privacy. If a mobile terminal uses a permanently allocated IP address, it may be possible to track the movement of the terminal in the Internet. Furthermore, the current location of a mobile terminal may be revealed if a dynamically allocated IP address is stored and associated with a subscriber (or terminal) identity in a location database in the Internet (e.g. a Domain Name System (DNS) server). It may therefore be possible for a hostile party to query the current location of a mobile terminal.